This invention relates to composing stereoscopic photographs and particularly to composing apparatus wherein multiple two-dimensional views of an object field are projected onto a photosensitive surface through a lenticular screen.
Our U.S. Pat. No. 3,953,869, issued Apr. 27, 1976, discloses methods and apparatus for producing stereoscopic photographs. In one form of apparatus there disclosed, stereoscopic photographs are produced using a multi-lens camera which simultaneously takes a plurality of two-dimensional views of an object field, each view from a different horizontal vantage point. The images taken by the camera are located side-by-side on a film strip with the spacing between adjacent views determined by the center-to-center spacing of the camera lenses. A stereoscopic photograph is produced from these adjacent two-dimensional views by projecting the images onto a photosensitive print film over which is placed a lenticular screen. To achieve proper stereoscopic or three-dimensional image appearance, the image on each of the two-dimensional views of a selected object in the object field is projected in registry with a reference point. The selected object will thus appear to lie in the plane of the stereoscopic photograph, while objects closer to the camera than the selected object will appear to project from the photograph and objects located farther from the camera than the selected object will appear to recede into the photograph.
In accordance with U.S. Pat. No. 3,953,869, for proper image composition in the stereoscopic photograph the two-dimensional views and projection lenses are so arranged relative to the lenticular screen that the condensed images formed therefrom beneath each lenticule of the screen are equidistantly and symmetrically spaced across the width of the lenticule; see FIG. 3 of the patent. Moreover, for optimum image quality in the final picture, the overall angle at which the two-dimensional views are projected onto the lenticular screen should substantially equal the viewing or acceptance angle of the lenticular screen. It is not practical in certain applications, however, such as in the case of snap-shot cameras, for example, to utilize a two-dimensional film strip of sufficient length to allow the foregoing composing conditions to be achieved without unduly enlarging the size of the camera.
U.S. Pat. No. 3,953,869 discloses alternate techniques for overcoming this problem and achieving the required projection lens spacing and projection angle in the composing step. According to one such technique, the two-dimensional film strip is cut and the individual views, together with the associated projection lenses, are physically separated by the required distance. Another technique is to project the two-dimensional views sequentially, i.e., one at a time, and move the film strip between projections of successive two-dimensional views.
Although these composing techniques are useful for certain applications, it is desirable in other applications, particularly where composing speed is important or where large numbers of film strips are to be handled, to avoid the necessity of cutting the film strip and separately locating the individual two-dimensional views and projection lenses in the proper projecting positions. For like reasons, it is desirable to avoid the repeated movement and projection of the film strip required in the sequential composing technique.
As is further disclosed in U.S. Pat. No. 3,953,869, adjustments are required either in the camera or the composing apparatus whenever there is a change in the distance from the camera to the selected object, designated the "key subject matter" in the patent, if optimum image quality is to be obtained in stereoscopic photographs. The patent discloses cameras having structure for accomplishing such adjustments within the cameras themselves, thereby allowing the composing apparatus to be fixed. In order to minimize camera complexity and cost, however, it is desirable that the adjustments be carried on in the composing apparatus. This is especially true for snapshot cameras and the like, where the cameras must be at once easy to handle and use and inexpensive.